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Steam Cylinder.                            257

XXIX, Steam Cylinder (Fig. 263).—The various opera-
tions are shewn at Fig. 264. The ends are first bridged, and the
centre found by reference to the outer curve of the cylinder flange.
Mark temporarily the height of the centre B. Adjust until the
top of the cylinder foot is fairly level, giving and taking with the
three centres at A and B. Scribe the horizontal centre line, B B,
all round, and square up the vertical line, c c; then strike the
circle D for boring. Line the heights of the steam and exhaust
flanges at E, and scribe the thickness of the foot at F ; line also
the thickness G of the bosses for the bolts. Scribe the height of
the valve-guide H, using a special piece of bent wire for the
scriber as shewn, and mark the heights, j, of the indicator

Set the cylinder upside down, as at M, and plane the foot.
Set upright, as at N, and plane the steam and exhaust flanges,
the indicator bosses, and the foot bosses. Now clamp between
angle plates on the planing machine as at p, and if these be
true vertically (as they should be) there will be no difficulty in
packing correctly; but if not, some care must be exercised, and
in any case the centre of the cylinder must be levelled longitudi-
nally. Scribe the steam chest face to correct distance from
cylinder centre, and plane with a front tool, p. At the same
setting the valve face may be planed at Q with long, strong side
tools, right and left, and the valve-guide also finished.

The cylinder must next be bored. This is done by packing
up, as at K, on a horizontal boring^iachine of the type described
on page-i6i, but of a smaller pattern. Bore right through, and
face the flanges by first measuring through the cylinder, as at j-.,
so as to leave an equal amount of seating on each flange; then
alter the tool to take out the bell mouth or larger diameter at
each end. Set the casting on end, as at o, and plane the stuffing-
box seatings so as to be level with the cover seating.

All the main faces are now machined, and the rest of the
lining may be done. At v the inner square is scribed on the
steam chest face, measuring from the horizontal, and vertical
centres, the latter being squared up with reference to tHe outer
edge of the flange. Take the material out by hand, or by slotting
tool, very probably the former. The steam chest coyer may be